This nonprovisional application claims priority under 35 U.S.C. xc2xa7 119(a) on Patent Application No. 2001-400674 filed in JAPAN on Dec. 28, 2001, which is herein incorporated by reference.
This application is related to Japanese Patent Application No. 2001-400674 filed on Dec. 28, 2001, whose priority is claimed under 35 USC xc2xa7119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to an LED (light emitting diode) display panel and an LED display apparatus. More particularly, it relates to an LED display panel and an LED display apparatus which are suitable for conveying information such as used for a traffic information bulletin board.
2. Description of Related Art
LED display apparatus using LED display panels are employed for traffic information bulletin boards and the like. An LED display panel is constructed to include a plurality of LEDs arranged in columns and rows to form a so-called dot matrix and is adapted to display characters, figures and others by activation of some of the LEDs using a dynamic drive circuit composed of transistors, for example.
A dynamically driven LED display apparatus known conventionally is described with reference to FIG. 7 and FIG. 8.
As shown in FIG. 8, in the display panel having LEDs regularly arranged in columns and rows in the matrix (e.g., n rowsxc3x97n columns), the LEDs (L11, L12, . . . , L1n, L21, L22, . . . , Ln1, Ln2, . . . , Lnn) are connected in a matrix in such a manner that they are located between column lines (referred to as X lines 52, each line being indicated as X1, X2, . . . , Xn) and row lines (referred to as Y lines 54, each being indicated as Y1, Y2, . . . , Yn). More particularly, n LEDs L11, L12, . . . , L1n are connected sequentially from line X1 to line Xn along line Y1, n LEDs L21, L22, . . . , L2n are connected along line Y2, and n LEDs Ln1, Ln2, Lnn are connected along line Yn.
Either the X lines 52 or the Y lines 54 are connected to output terminals of a lighting data drive circuit for transmitting lighting data, and the lighting data is transmitted to each LED from the lighting data drive circuit. The other lines are connected to output terminals of a scanning drive circuit and are sequentially scanned line by line.
FIG. 7 is a block diagram illustrating the construction of driving circuits for driving the LED display apparatus shown in FIG. 8. In FIG. 7, column lines (X lines 52) are lighting data input lines, and row lines (Y lines 54) are scanning lines (also referred to as common lines). In the figure, LEDs (L11 to Lnn) are arranged in a matrix on a display panel 60, LEDs in the respective columns are linearly connected by lines X1 to Xn corresponding to the columns, and LEDs in the respective rows are linearly connected by lines Y1 to Yn corresponding to the rows.
The lines X1 to Xn are connected to output terminals a1, a2, . . . , an of a lighting data drive circuit (X line drive circuit) 62. Lighting data about characters and the like to be displayed on the display panel is input to the lighting data drive circuit 62. The lighting data drive circuit 62 includes a shift register, a latch and a luminance adjusting circuit. The lighting data transmitted via a signal line is input to the shift register in timing with a clock pulse (not shown). The data of each of the lines X1 to Xn (data for one scanning line) is latched for a predetermined time, and shifted in the next timing. New lighting data (data for the next one scanning line) is sequentially input to the shift register. Thus lighting data necessary for forming one picture is stored in the shift register.
On the other hand, the lines Y1 to Yn are connected to output terminals of a scanning drive circuit (Y line drive circuit) 64 whose input side is connected to a decoder 66.
Address signals are input to the decoder 66 from address line A0, A1, A2, A3. Address signal values transmitted from the address lines are set to increment. When the address signal values are input to the decoder 66, the output from the decoder 66 is input to the scanning drive circuit 64 to turn the line Y1 on first. When a predetermined time has elapsed by count of a clock pulse (not shown), the line Y1 is turned off and the line Y2 is turned on. This operation is repeated until the line Yn is turned on, and then the line Y1 is turned on again. This process is repeated in the same manner. Thereby the row lines (Y lines) are scanned.
Therefore, by synchronizing the timing of data shift by the lighting data drive circuit (X line drive circuit) 62 and the timing of scanning by the scanning drive circuit (Y line drive circuit) 64, the entire one picture can be displayed. Two hundred fifty times of scanning per second realize the display of the picture without flickers.
In the LED display apparatus of the dynamic drive system as described above, if one of the scanning lines (common lines), for example, the line Y1, is out of order, all LEDs in one row connected to the line Y1 do not illuminate.
LED display apparatus for traffic information bulletin boards are often used continuously under any weather condition day and night, and with such apparatus, failures cannot be avoided completely.
For this reason, even if a failure occurs, what should be avoided most is that the failure makes the contents of information displayed on the apparatus unable to be understood at all.
Accordingly, an object of the present invention is to provide an LED display panel and an LED display apparatus which are adapted to allow reasoning by analogy the contents of displayed information such as characters or the like from dots (LEDs) capable of lighting even if a drive circuit or a line of the LED display panel fails and non-lighting dots (LEDs which are in a non-lighting state) result from the failure.
Also an object of the present invention is to provide an LED display panel and an LED display apparatus which can report a failure to urge the shooting of the failure if a drive circuit, a line or the like thereof is out of order.
The LED display panel (a) of the present invention is characterized by comprising a plurality of LEDs arranged in a matrix, a plurality of lighting data lines connecting the LEDs in either one of a row direction and a column direction, and a plurality of scanning lines connecting the LEDs in the other one of the row direction and the column direction, at least either the lighting data lines or the scanning lines connecting the LEDs such that the lighting data lines or the scanning lines form groups of at least two lines crossing in a staggered configuration.
The LED display apparatus of the present invention is characterized by comprising (a) the LED display panel as described above, (b) a lighting data drive circuit having a plurality of lighting data output terminals for transmitting lighting data to the lighting data lines of the LED display panel which are connected to the lighting data output terminals, and (c) a scanning drive circuit having a plurality of scanning output terminals for sequentially scanning the scanning lines of the LED display panel which are connected to the scanning output terminals.
According to the present invention with the above-mentioned construction, since the LEDs are so arranged that either the lighting data lines or the scanning lines connect the LEDs in such a manner that the lighting data lines or the scanning lines form the groups of at least two lines in the staggered configuration, all LEDs on one column or row cannot fall wholly in the non-lighting state even if a failure occurs.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.